The invention relates to the field of methods and systems for estimating the height of the gravity center of a vehicle.
For more and more vehicle applications, such as the electronic safety systems controlling the vehicle's dynamics (such as brake anti-blocking systems, electronic stability programs, etc. . . . ) it has become a strong improvement to be able to determine the position of the gravity center of a vehicle. This is even more crucial in the field of trucks where, depending on whether it is loaded or pnloaded, the position of the vehicle's gravity center may vary considerably.
Therefore, there have been suggested several methods and devices for determining the position of the center of gravity, including its height. However, all these methods require that special sensors are used which are not typically present in a vehicle, thereby increasing the price of the system. For example, on a vehicle equipped with air suspension, some methods require pressure sensors in each air cushion to determine the instant vertical load on each wheel. Such sensors can of course not be used on vehicle having more traditional mechanical suspensions.
Therefore, it is desirable to provide a new method for estimating the height of the gravity center of a vehicle, which uses only the sensors and/or information which are available on most of today's modern trucks
An aspect of the invention provides for a method for estimating the height of the gravity center of a vehicle having at least a front axle and a rear axle each carrying at least two wheels, comprising the steps of
a) determining a first braking period and a second braking period occurring along road portions having substantially the same slope, but where the first and second braking periods result in different vehicle decelerations, and during both braking periods, estimating at least the following variables:                vehicle acceleration (Acc);        the wheel slippage rate (WSR) for the front and rear axles;        the braking forces (Bkf) or braking torque at each of the front and rear axles, or a ratio thereof (K); and        the slope (Slp) of the corresponding road portion;b) estimating, using only the estimations of step a) made during both periods, the vehicle center of gravity height (H).        
The features and advantages of the present invention are well understood by reading the following detailed description in conjunction with the drawing which is a flow chart illustrating steps in a method according to an aspect of the present invention.